This invention relates in general to vehicular drive train systems including a driveshaft assembly for transferring rotational power from an engine/transmission assembly to an axle assembly. In particular, this invention relates to an improved structure for a component for use in such a vehicular driveshaft assembly and to a method of manufacturing same.
In most land vehicles in use today, a drive train system is provided for transmitting rotational power from an output shaft of an engine/transmission assembly to an input shaft of an axle assembly so as to rotatably drive one or more wheels of the vehicle. To accomplish this, a driveshaft assembly is connected between the output shaft of the engine/transmission assembly and the input shaft of the axle assembly. In some vehicles, the distance between the output shaft of the engine/transmission assembly and the input shaft of the axle assembly is relatively short. In these vehicles, the driveshaft assembly can include a single, relatively long driveshaft tube, the ends of which can be connected to the output shaft of the engine/transmission assembly and the input shaft of the axle assembly by respective universal joints. Such universal joints are well known in the art and provide a rotational driving connection therebetween, while accommodating a limited amount of angular misalignment between the rotational axes of the various shafts. In other vehicles, the distance between the output shaft of the engine/transmission assembly and the input shaft of the axle assembly is relatively long, making the use of a single driveshaft tube impractical. In these vehicles, the driveshaft assembly can include a plurality (typically two) of separate, relatively short driveshaft tube sections. The inner ends of the driveshaft sections are connected together by a first universal joint, and the outer ends of the driveshaft sections are connected to the output shaft of the engine/transmission assembly and the input shaft of the axle assembly by second and third universal joints.
It is known that a small amount of relative axial movement frequently occurs between the engine/transmission assembly and the axle assembly when the vehicle is operated. Because of this, it is often desirable that both single and multiple section driveshaft assemblies be capable of accommodating a limited amount of relative axial movement between the outer ends thereof. To accomplish this, it is known to incorporate a slip yoke assembly within the driveshaft assembly. A typical slip yoke assembly includes a slip tube shaft that is connected to one end of the driveshaft tube (or one end of one of the driveshaft tube sections) and a slip yoke that is connected to one of the universal joints. The slip tube shaft has an externally splined portion that cooperates with an internally splined portion of the slip tube yoke so as to provide a rotational driving connection therebetween, while permitting a limited amount of relative axial movement to occur.
Traditionally, the various components of the driveshaft assembly have been manufactured from steel. Steel is a relatively strong and inexpensive material that is commonly available. However, steel is relatively heavy in weight, which is disadvantageous from a fuel economy standpoint. To address this, it is known to manufacture some of the components of the driveshaft assembly from aluminum, which is a relatively strong and lightweight material. However, aluminum has a relatively low melting temperature in comparison to steel. As a result, it has been found to be relatively difficult to weld or otherwise secure aluminum driveshaft components to steel driveshaft components. Accordingly, it would be desirable to provide an improved structure for a component for use in a vehicular driveshaft assembly, and a method of manufacturing same, that facilitates the use of diverse materials, such as steel and aluminum.
This invention relates to an improved structure for a component for use in a vehicular driveshaft assembly, and a method of manufacturing same, that facilitates the use of diverse materials, such as steel and aluminum. The driveshaft component includes a tube yoke formed from a first material and having a hollow cylindrical sleeve portion extending co-axially therefrom. A first end of a driveshaft tube, also formed from the first material, is disposed telescopically about the sleeve portion of the tube yoke and is secured thereto using conventional welding processes or other techniques that are suited for joining components formed from similar materials. The driveshaft component further includes a transition member that is also preferably formed from the first material. The transition member includes a main body portion having a hollow cylindrical sleeve portion that extends co-axially therefrom. The main body portion of the transition member is preferably formed having a wall thickness that is greater than the wall thickness of the sleeve portion. A second end of a driveshaft tube is disposed telescopically about the sleeve portion of the transition member and is secured thereto using conventional welding processes or other techniques that are suited for joining components formed from similar materials. Lastly, the driveshaft component includes a slip tube shaft that is preferably formed from a second material that is different from the first material. To facilitate the securement to the transition member, the slip tube shaft is formed having an enlarged end portion that is generally hollow and cylindrical in shape, having an outer diameter and a wall thickness that are approximately equal to the outer diameter and wall thickness of the main body portion of the transition member. The enlarged end portion of the slip tube shaft is secured to the main body portion of the transition member using a process that is suited for joining components formed from dissimilar materials, such as by friction welding. The increased wall thickness of the main body portion of the transition member facilitates the performance of the friction welding process because the increased wall section""s ability to resist tearing from the velocity induced shear stress during the frictional heat generation and forging operation at welding. However, because the driveshaft tube is formed from the same or similar material as the transition member, it can be secured thereto using conventional welding processes as described above. Consequently, the wall thickness of the driveshaft tube can be maintained at a minimum throughout the length thereof so as to minimize the overall weight of the driveshaft assembly.
Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings.